Patients with end stage renal disease (ESRD) must routinely receive dialysis treatments in order to live. Indwelling catheters are a useful dialysis access method for hemodialysis because they reduce the number of vein penetrations needed for repeated dialysis. Chronic central venous catheters for dialysis (CVCD) are the major long-term dialysis access for over 25% of ERSD patients or hemodialysis.
In a standard flow-through dialysis system, the CVCD must provide a first route for removal of blood and a second route for return of blood at a rate of at least 300 ml/min. A CVCD for a standard flow-through dialysis system can be formed by inserting two separate catheters into the jugular vein in a manner that forms a tunnel over the clavicle. In this arrangement, the catheter tips rest near the junction of the superior vena cava with the right atrium. The tip of the blood removal catheter, or arterial catheter, is placed 3-4 cm above the tip of the downstream blood return catheter, or venous catheter, in order to prevent mixture of cleansed blood with blood entering the arterial catheter.
As an alternative to the separate catheter for the standard flow-through dialysis system, a single-bodied catheter with two separate lumens can be used for dialysis access. In this arrangement, the tip of the arterial lumen is placed 3-4 cm above the tip of the venous lumen. Like the standard flow-through arrangement, this arrangement also prevents mixture of cleansed blood with blood entering the arterial lumen. As yet another alternative, dialysis can also be performed by using a single catheter with a single lumen. In this case, the dialysis machine delivers a quantity of untreated blood and then returns treated blood in alternating cycles.
Blood enters and exits the catheter lumen through ports or holes in the catheter. The design of these ports is highly variable, and similar concepts are employed in both single and dual lumen catheters. A first example is a catheter lumen having a single port at the tip for entrance or exit of blood. A second example is a catheter lumen having a blood exchange port located on the side of the lumen body toward its distal tip. Another example is a catheter lumen having multiple blood exchange ports axially placed around the side of the lumen body toward its distal tip. While all of the above CVCD designs work, there is room for improvement in the field, and there are problems with all current port designs for dialysis catheters.
Arterial catheter lumens that contain only one blood exchange port, no matter its location, run the risk of obstruction of the port by neighboring vein walls, by blood clotting in the exchange port, and by growth of a fibrin sheath around the distal end of the lumen and exchange port. Venous catheter lumens that contain only one blood exchange port, no matter its location, run the risk of obstruction by blood clotting in the exchange port and by growth of a fibrin sheath around the distal end of the lumen and the exchange port. Obstruction of the blood exchange port prevents the desired blood exchange rate of at least 300 ml/min from occurring. The degree of obstruction may render the indwelling catheter(s) ineffective for dialysis access. Therefore, when this level of obstruction occurs, the indwelling catheter(s) must be replaced.
Arterial catheter lumens containing multiple blood exchange ports around the distal end of the catheter reduce the occurrence of vein obstruction. However, the presence of multiple ports increases the risk of obstruction by blood clots because the multiple ports allow blood to flow into the lumen when idle, which can wash out the anticoagulant solution. The diminished presence of anticoagulant solution at the distal end of the catheter increases the amount of blood clotting in the ports and lumen. Obstruction of the blood exchange ports prevents the desired blood exchange rate of at least 300 ml/min from occurring. The degree of obstruction may render the indwelling catheter(s) ineffective for dialysis access. Therefore, when this level of obstruction occurs, the indwelling catheter(s) must be replaced.
Thus, there is a general need in the industry to provide methods and devices for the prevention of obstructions in the blood exchange ports of catheters and around the distal end of catheters. It is desired that these methods and devices prevent obstructions of the lumen due to clotting and fibrous sheath encasement of the tip of the catheter, as well as maintain the catheter anti-coagulant lock solution inside the lumen during idle periods between dialysis.